The present invention relates to an apparatus for adjusting the driving mode ride height of a vehicle having a pneumatic suspension system.
When load-carrying vehicles (LCV""s) are to be loaded and unloaded, they are normally brought to a loading dock. In order to facilitate and to increase the efficiency of such loading and unloading, the height of the loading dock should be adapted to the elevation of the loading platform of the LCV. One way of achieving this result is to construct a loading dock having a variable elevation. Such an approach may be economically feasible with highly utilized loading docks, such as goods terminals, where loading and unloading are very frequent.
Another method of solving the problem of adapting the height of the loading dock and the elevation of the LCV loading platform is to control the elevation of the vehicle loading platform. Such an approach has the advantage of allowing for adaptation to loading docks having a fixed height.
Such a system is described, for example, in British Patent No. 2,237,780.
This patent describes a system in which the LCV loading platform is located at a predetermined height when the vehicle is operated in its normal driving mode. When the vehicle is parked for loading and unloading, however, the elevation of the LCV loading platform is adjustable so as to allow for adaptation of its elevation to the height of the loading dock, thus enabling efficient loading and unloading. When the LCV is to once again be operated in a normal driving mode, the original fixed elevation of the LCV loading platform is restored.
PCT Application No. WO 91/07291 discloses another apparatus of the type disclosed above.
One problem exhibited by the prior art is that the height assumed by the LCV loading platform, when restoring the elevation of the LCV loading platform for normal operation of the LCV, after performing height adjustment during loading and unloading, is fixed and cannot be varied. Therefore, when the vehicle is operated in a normal driving mode, i.e. when the vehicle is not parked or is driven at a speed exceeding a relatively low speed, the elevation of the LCV loading platform in most cases cannot be adjusted, and in those cases where the elevation is adjustable, it is adjustable within the same range as the permitted range for loading and unloading. This initially means that control possibilities are not available, which is a disadvantage with this type of prior art, and secondly that the ride height in the driving mode is adjustable within a range where a risk of damage to the load and the LCV exists.
It has been determined by tests and calculations that the aerodynamic properties of an LCV are dependent on the elevation of the LCV loading platform. Such tests and calculations have shown that is preferable, for obtaining an LCV having a lower air resistance, and thus a lower fuel consumption, for the elevation of the LCV loading platform to be as low as possible when the vehicle is operated in a driving mode.
Thus, it is an object of the present invention, by providing the LCV with a possibility of adjusting the elevation of the LCV loading platform, to permit the vehicle to be operated in the driving mode with a low set driving mode elevation or ride height, thereby reducing both the air resistance and the fuel consumption.
A second advantage of being able to lower the elevation of the LCV loading platform is, in those cases where the absolute height of the LCV is limited by regulations or accessibility, that a larger loading height can be utilized, thereby improving the financial strength of the LCV.
Thus, another object of the present invention is, by providing the LCV with a mechanism to control the height of the loading platform, to ensure that the LCV can be driven with a low ride height, whereas the LCV can carry further load, which improves the economy for the LCV.
A further advantage of being able to lower the ride height of the LCV framework is that this lowers the cab instep height which increases driver comfort.
Thus, it is another object of the present invention, by providing the LCV with the ability of adjusting the ride height of the LCV framework, and thereby that of its loading platform and cab, which are affixed to the framework, to lower the cab instep height thereby increasing driver comfort.
An LCV loading platform is resiliently suspended by the structure carrying wheel axles and wheels. Thus, when the LCV is operated in the driving mode, the LCV loading platform will oscillate around the height level that the loading platform has assumed in an equilibrium position, when standing still. The amplitude of loading platform oscillations around its equilibrium position is dependent of the quality of the road, the load weight, the vehicle speed, and the characteristics of the loading platform suspension.
As discussed above, the loading platform of an LCV is fitted to the wheel-carrying structure by resilient means. Such resilient means display elastic properties within a certain range of expansion and compression. If the resilient means are compressed excessively, they will then act like a rigid connection. Such excessive compression will occur if the loading platform has been adjusted to an excessively low position when the LCV is operated in a driving mode. This means that the harmonic oscillation which, when the loading platform elevation is correctly adjusted, occurs around the equilibrium position of the loading surface height level, is replaced by an interrupted oscillation when the resilient means is compressed past its elastic range. When interrupted oscillatory motions take place, large accelerations occur, leading to the load, the resilient means, and the LCV as a whole, being subjected to very high stress forces. If the loading platform is adjusted to an excessively high position, problems will also occur, in that the resilient means may be extended in excess of the elastic range. In such cases, an interrupted oscillatory motion also occurs leading to high stress forces on the load, the resilient means, and on the LCV as a whole.
Yet another object of the present invention is to provide the LCV with a means of adjusting the elevation of its loading platform, thus allowing for adjustment within a first, larger range when the vehicle has taken up a parking or marshalling position, and adjustment within a second, smaller range when the vehicle has taken up a driving mode. Adjustment of the ride height will thus be allowed when the vehicle is in a driving mode, but the elevation or ride height in this mode can only be adjusted within a range which is not detrimental to either the load or the vehicle.
One advantage of allowing the ride height of the vehicle framework and loading platform to be adjusted to as high a level as possible is that the framework ground clearance increases. This is of importance when the vehicle is driven over bad ground and when the vehicle is driven across angled ramps and steep structures.
Still another object of the present invention is, by providing the LCV with a means of adjusting the elevation of the vehicle framework and loading platform, that the driver will be able to selectively adjust the ride height in accordance with various conditions. Thus, if the vehicle is to be driven on a flat road as low a ride height as possible is of interest, or if the vehicle is driven over bad ground or across steep ramps and structures, as high a ride height as possible is of interest.
A still further advantage of having the vehicle framework and loading platform adjustable within a first, larger range when the vehicle has taken up a parking or marshalling position and a second smaller range when the vehicle has taken up a driving mode is that the vehicle cardan shaft, which is provided for connecting an output shaft of a transmission arranged in the vehicle to a driving wheel axle, is connected to the driving wheel axle in a certain angular position. When the vehicle is standing still or being driven at low speed, a relatively large deviation from this position is allowable. When the vehicle is driven at a higher speed, only a smaller deviation from this angular position is allowable. As the cardan shaft is carried by the same structure that carries the vehicle loading platform, that is the vehicle framework or frame structure, the elevation of the framework, the frame structure, or the loading platform, must only be adjustable within a smaller range when in the driving mode.
It is also an object of the present invention by providing the LCV with a means of adjusting the elevation of its loading platform, thus allowing adjustment within a first, larger range when the vehicle has taken up a parking or marshalling position, and within a second smaller range when the vehicle has taken up a driving mode to allow adjustment of the ride height when the vehicle is in the driving mode, at the same time allowing the ride height only to be adjusted within a range that is not detrimental to the cardan shaft and its suspension.
In accordance with the present invention, these and other objects have now been realized by the invention of apparatus for adjusting the height of a vehicle frame on a vehicle including a vehicle suspension system, the apparatus comprising vehicle frame elevation adjustment means for adjusting the elevation of the vehicle frame, and control means for controlling the vehicle frame elevation adjustment means, the control means adapted to be set in a first mode corresponding to normal driving of the vehicle and a second mode corresponding to parking or marshalling of the vehicle, whereby when the control means is in the first mode the vehicle frame elevation adjustment means permits adjustment of the vehicle frame within a first range and when the control means is in the second mode the vehicle frame elevation adjustment means permits adjustment of the vehicle frame within a second range, the first range being greater than the second range, and the second range being within the first range.
In a preferred embodiment, the vehicle frame elevation adjustment means comprises a pneumatic suspension system for the vehicle. Preferably, the vehicle includes at least one wheel axle, and the vehicle frame elevation adjustment means adjusts the elevation of the vehicle frame with respect to the at least one wheel axle.
In accordance with a preferred embodiment of the apparatus of the present invention, the pneumatic suspension system is arranged between the vehicle frame and the at least one wheel axle, the control means including selector means for selecting one of the first and second modes, and the pneumatic suspension system including a source of compressed air, valve means for selectively feeding the compressed air to the pneumatic suspension system or drawing the compressed air from the pneumatic suspension system in response to the control means, whereby the pneumatic suspension system is expanded or compressed in order to adjust the distance between the vehicle frame and the at least one wheel axle, the distance between the vehicle frame and the at least one wheel axle being adjusted within the first range when the control means is in the first mode and within the second range when the control means is in the second mode. Preferably, the apparatus includes measuring means for measuring the distance between the vehicle frame and the at least one wheel axle.
In accordance with one embodiment of the apparatus of the present invention, the measuring means comprises an angular position sensor, a lever connected to the angular position sensor, and a control rod articulated with respect to the lever, the angular position sensor being attached to one of the vehicle frame and the at least one wheel axle and the control rod being attached to the other of the vehicle frame and the at least one wheel axle, whereby the angular position sensor measures the angular position of the lever so that when the distance between the vehicle frame and the at least one wheel axle is altered by means of the pneumatic suspension system the position of the control rod is altered, thereby altering the angular position of the lever sensed by the angular position sensor, the control means including means for reading the angular position of the lever and determining the distance between the vehicle frame and the at least one wheel axle based thereon.
In accordance with a preferred embodiment of the apparatus of the present invention, the pneumatic suspension system includes air bellows comprising a flexible material, a base for the air bellows, and a top for the air bellows, the air bellows, the base and the top defining a closed space, and passage means connecting the valve means with the closed space, the pneumatic suspension system including a cylindrical surface, whereby the bellows is adapted to roll onto the cylindrical surface when the pneumatic suspension system is compressed and to roll off of the cylindrical surface when the pneumatic suspension system is extended. Preferably, the cylindrical surface is incorporated in the base, and the base is attached to the at least one wheel axle. In a preferred embodiment, the cylindrical surface comprises a hollow body, whereby the volume of the closed space is increased.
In accordance with one embodiment of the apparatus of the present invention, the apparatus includes selector means connected to the control means, the selector means being manually settable between the first mode and the second mode.
In accordance with another embodiment of the apparatus of the present invention, the apparatus includes vehicle speed detection means for detecting the speed of the vehicle, whereby the control means is set in the first mode when the speed of the vehicle is greater than a predetermined speed and the control means is set in the second mode when the speed of the vehicle is below the predetermined speed. Preferably, the predetermined speed is 0 km/hour, and in another embodiment the predetermined speed is 20 km/hour.
In accordance with another embodiment of the apparatus of the present invention, the limits of the first range are defined by the maximum extension and compression of the pneumatic suspension system.
In accordance with another embodiment of the apparatus of the present invention, the vehicle includes a cardan shaft, and the limits of the second range are defined by the maximum and minimum angle of the cardan shaft and by a required upward and downward suspension stroke.
In accordance with the present invention, apparatus has also been provided for adjusting the distance between a vehicle frame and at least one wheel axle of a vehicle having a suspension system, the apparatus comprising a control unit including control members for setting a desired value for the distance, control means adapted to be set in a first mode and a second mode, and selector means for selecting one of the first and second modes for the control means whereby when the control means is in the first mode the desired value for the distance is within a first range and when the control means is in the second mode the desired value for the distance is within a second range, the first range being greater than the second range, and the second range being within the first range. In a preferred embodiment, the vehicle includes a cab and wherein the control means is attachably mounted in the cab.
In accordance with one embodiment of the apparatus of the present invention, the first mode corresponds to normal driving of the vehicle and the second mode corresponds to parking or marshalling of the vehicle. In another embodiment, the selector means comprises a manual switch.
In order to achieve the above objects of the present invention, apparatus is thus provided for adjustment of the driving mode elevation of a vehicle, where the vehicle elevation is adjustable within a second, smaller range when the control device has taken up its driving mode, the second smaller range lying within the first, larger range for the parking or marshalling mode.
In one embodiment of the present invention, pneumatic suspension means arranged on the vehicle are utilized as the means changing the height level of the vehicle for adjustment of the distance between the wheel axle of the vehicle and the vehicle load-carrying structure, and thereby the elevation of the vehicle loading platform. According to these embodiments, mounting of further height regulation means are avoided which is space, weight and resource saving.
In one embodiment of the present invention, measuring means are used for determination of a measurement of the distance between the wheel axle and the load-carrying structure, which means that a more exact control of the elevation of the frame structure and the loading platform can be achieved.
According to another embodiment of the present invention, a control unit is provided for adjustment of the distance between a load-carrying structure and at least one wheel axle of a vehicle, where the distance is adjustable within a first, larger range when an integral control device in the vehicle has taken up its parking or marshalling mode, and the vehicle ride height is adjustable within a second, smaller range when the control device has taken up its driving mode, the second smaller range lying within the first, larger range.
xe2x80x9cDriving mode ride heightxe2x80x9d refers to the elevation of the loading platform when the LCV is operated in the driving mode.